A number of prior inventors have devised retractable ramps which can be stowed beneath the floor of a motor vehicle and deployed through a door opening to provide a slightly inclined surface extending from the pavement to the vehicle floor. Such ramps greatly facilitate the entry into the vehicle of a wheelchair-bound person. These ramps are usually extended and retracted by a motorized drive system powered from the vehicle's electrical system.
One such ramp system which has had reasonable commercial acceptance is disclosed in United States Patent No. 4,827,548, granted May 9,1989, to Delos W. Hood for "Vehicle Entrance Ramp". A significant shortcoming of this particular ramp system is the absence of any mechanism permitting manual deployment and stowage of the ramp in the event of a power failure or failure of the motorized drive system.
Interestingly, this same inventor, Mr. Hood, earlier devised a different ramp structure which did incorporate a releasable connecting mechanism to permit the ramp to be manually moved independently of the motorized drive. U.S. Pat. No. 4,759,682, granted Jul. 26, 1988, for "Vehicle Entrance Ramp" discloses this ramp structure. Unfortunately, the releasable connecting mechanism there disclosed appears to be cumbersome to operate. The mechanism itself is complex and is accessible for reconnection only with the ramp in its fully extended position. Thus, if the ramp has been manually stowed, it must be manually fully extended before powered operation can be resumed.
There continues to be a need for a retractable ramp system which can quickly and easily be converted from powered operation to manual operation and back to powered operation.